Method of controlling particles size of fillers in extrudable compositions, compositions comprising the fillers and devices made from the compositions

ABSTRACT

A method of controlling a particle size distribution of a filler in an extrudable composition comprises introducing an extrudable composition comprising a polymer matrix material and a filler into an extruder, the filler having a first average particle size that is larger than a target average particle size. The extrudable composition is extruded one or more times using the extruder to reduce the size of the filler from the first average particle size to a reduced average particle size, the reduced average particle size being within 10% of the target average particle size.

This Project Agreement Holder (PAH) invention was made with U.S.Government support under Agreement No. W15QKN-14-9-1002 awarded by theU.S. Army Contracting Command New Jersey (ACC-NJ) Contracting Activityto the National Advanced Mobility Consortium. The Government has certainrights in the invention.

DETAILED DESCRIPTION Field of the Disclosure

The present disclosure is directed to a method of controlling the sizeof filler particles in an extrudable composition, extrudablecompositions comprising the fillers and devices made from the extrudablecompositions.

BACKGROUND

Obtaining predetermined particle size distribution for nanosizedparticles from commercial, off the shelf fillers or additives is oftennot reliably possible. Sources of fillers, such as, for example, carbonblack, generally have a large particle size and/or a wide sizedistribution. Variability of filler size distributions from sample tosample makes processing difficult. Due to this variability, it is oftendifficult and expensive to make compositions having specific particlesize distributions.

Various techniques are known in the art for making optical materialsthat employ nano-sized and micron sized particles as fillers. Forexample, milling carbon to form particles and extruding compositionscomprising such carbon particles is a known technique for making glasslenses. Known systems and techniques for forming optical elements havingpredetermined particles sizes often use a solution-based system. Forexample, solution-based systems for making optical filters are known.However, solution-based techniques often employ continuousstirring/mixing to maintain the particles suspended in solution, whichresults in increased cost and process complexity.

Novel techniques for forming materials with desired nano- andmicron-sized particle distributions that enable use of off-the-shelffillers would be a welcome improvement in the art. Additionally,composite materials that include fillers that can handle very high andvery low temperature would also be a welcome step forward in the art.

SUMMARY

An implementation of the present disclosure is directed to a method ofcontrolling a particle size distribution of a filler in an extrudablecomposition. The method comprises introducing an extrudable compositioncomprising a polymer matrix material and a filler into an extruder, thefiller having a first average particle size that is larger than a targetaverage particle size. The extrudable composition is extruded one ormore times using the extruder to reduce the size of the filler from thefirst average particle size to a reduced average particle size, thereduced average particle size being within 10% of the target averageparticle size.

Another implementation of the present disclosure is directed to afilter. The filter comprises a support substrate. A film is disposed onthe support substrate, the film comprising a polymer matrix material anda filler. The filler has a particle size distribution configured tofilter a desired range of wavelengths of light, the particle sizedistribution having been achieved by extrusion.

Still another implementation of the present disclosure is directed to anextrudable composition. The extrudable composition comprises a polymermatrix material and a filler. The filler has an average particle sizeranging from about 1 nm to about 700 nm and a concentration ranging from0.001 weight % to 0.3 weight %, relative to the total weight of theextrudable composition.

Yet another implementation of the present disclosure is directed to amethod of controlling a particle size distribution of a filler in anextrudable composition. The method comprises determining a targetaverage particle size for the filler and determining a targetconcentration of the filler. A first extrudable composition comprising apolymer matrix material and the filler is introduced into an extruder,the filler having a first average particle size that is larger than thetarget average particle size, the filler being at a concentrationranging from about 0.01 weight % to about 40 weight %, relative to thetotal weight of the extrudable composition. The first extrudablecomposition is extruded one or more times to reduce the size of thefiller from the first average particle size to a reduced averageparticle size to thereby form a second extrudable composition. Thereduced average particle size is within 10% of the target averageparticle size. The second extrudable composition is extruded with adiluent polymer to dilute the concentration of the filler to form athird extrudable composition having the target concentration.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the present teachings, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrates aspects of the present teachingsand together with the description, serve to explain the principles ofthe present teachings.

FIG. 1 is a flowchart of a method of controlling a particle sizedistribution of a filler in an extrudable composition, according to anaspect of the present disclosure.

FIG. 2 illustrates a schematic cross-sectional view of a filter,according to an aspect of the present disclosure.

FIG. 3 shows an example extruder screw design, according to an aspect ofthe present disclosure.

FIGS. 4A, 4B, 4C and 4D show FIB-SEM analysis of carbon black filled PVBpellets having 1 wt. % carbon black in PVB, according to an example ofthe present disclosure.

FIGS. 5A, 5B, 5C and 5D show FIB-SEM analysis of carbon black filled PVBpellets having 0.5 wt. % carbon black in PVB, according to an example ofthe present disclosure.

FIGS. 6A, 6B, 6C and 6D show FIB-SEM analysis of carbon black filled PVBpellets having 0.15 wt. % carbon black in PVB, according to an exampleof the present disclosure.

FIG. 7 shows spectral transmission for carbon black filled PVB pelletshaving 0.15 wt. % carbon black in PVB, according to an example of thepresent disclosure.

FIG. 8 shows the calculated spectral absorption coefficients for thethree spots plus average and standard deviation for carbon black filledPVB pellets having 0.15 wt. % carbon black in PVB, according to anexample of the present disclosure.

FIG. 9 shows transmission versus wavelength data collected for films ofvarious thickness that were pressed from 0.5% carbon black loaded PVB,according to an example of the present disclosure.

FIG. 10 shows absorption coefficient versus wavelength data calculatedfrom transmission data collected for films of various thickness thatwere pressed from 0.5% carbon black loaded PVB, according to an exampleof the present disclosure.

FIG. 11 shows a ratio of 0.15% carbon loading/0.5% carbon loading forabsorption coefficient verses wavelength, according to an aspect of thepresent disclosure.

FIG. 12 shows a plot of the particle loading versus AbsorptionCoefficient data shown in FIG. 11, according to an aspect of the presentdisclosure.

FIG. 13 shows an FESEM photomicrograph collected at 50,000×magnification for a carbon doped PVB film, made according to the methodsof the present disclosure.

FIG. 14 shows an FESEM photomicrograph image collected at 50,000×magnification using a contrast of ˜60% and brightness ˜0% for a carbondoped PVB film, according to an example of the present disclosure.

FIG. 15 shows an example inversion of an FESEM image, according to anexample of the present disclosure.

FIG. 16 shows the analysis conducted using the lowest carbon black areaof 300 nm² so it analyzes Feret's diameter >25 nm, according to anexample of the present disclosure.

FIG. 17 shows the major and minor axis of an ellipse employed inparticle analysis in the examples of the present disclosure.

FIG. 18 shows circularity values for some of the actual carbon blackimages, according to examples of the present disclosure.

FIG. 19 shows an example of Feret's diameter, as employed in theexamples of the present disclosure.

It should be noted that some details of the figures have been simplifiedand are drawn to facilitate understanding rather than to maintain strictstructural accuracy, detail, and scale.

DESCRIPTION

Reference will now be made in detail to the present teachings, examplesof which are illustrated in the accompanying drawings. In the drawings,like reference numerals have been used throughout to designate identicalelements. In the following description, reference is made to theaccompanying drawings that form a part thereof, and in which is shown byway of illustration specific examples of practicing the presentteachings. The following description is, therefore, merely exemplary.

It is understood by those skilled in the art that twin screw extrudershave small spaces between the twin screws, which can break down veryfine particles. While extruders have generally been used to reduceparticle size and mix/disperse very fine particles in polymercomposites, extruders have not been employed to repeatably andcontrollably provide targeted particle size distributions for nano-sizedand micron-sized particles in extrudable compositions in the past.

The methods of the present disclosure allow for forming materials withdesired nano-sized and micron-sized particle size distributions usingoff-the-shelf fillers that do not have the desired particle sizedistributions. The methods of the present disclosure provide for uniformmixing of nano-sized and micron-sized particles at low concentrations,such as below 1 wt % particle loading based on the total weight of thecomposition. The composition materials can, among other things, act aslight filters for reducing the intensity of light passing through thefilter.

The present disclosure is directed to a method 100 of controlling aparticle size distribution of a filler in an extrudable composition, asillustrated in the flowchart of FIG. 1. For purposes of the presentdisclosure, the particle size is defined as the Feret's diameter, whichis determined as described herein below. The phrase “average particlesize”, as used herein, is defined to be the mean size of the particledistribution based on Feret's diameter, as is also discussed in greaterdetail below.

As shown at 102 of FIG. 1, the method comprises determining a targetaverage particle size for the filler. The term “determining” as usedherein is defined broadly to include arriving at a value for the averageparticles size by any suitable means, including using mathematicalcalculations, experimentation, choosing of a desired value fromreference materials or receiving or otherwise obtaining a preselectedvalue from a third party. Referring to 104 of FIG. 1, the method furtherincludes introducing an extrudable composition comprising a polymermatrix material and a filler into an extruder. The filler has a firstaverage particle size that is larger than the target average particlesize. Whether the first average particle size is larger can bedetermined by comparing the first average particle size and the targetaverage particle size (both being based on Feret's diameter as discussedherein). The extrudable composition is then extruded one or more timesusing the extruder to reduce the size of the filler from the firstaverage particle size to a reduced average particle size, the reducedaverage particle size being within 10% of the target average particlesize.

The target average particle size can be any desired size that willprovide the desired benefits for which the filler is intended. As anexample, the target average particle size can range from about 1 nm toabout 700 nm, such as about 10 nm to about 500 nm, or about 50 nm toabout 400 nm, or about 100 nm to about 200 nm. Particle sizes withinthese ranges have certain benefits, depending on the application inwhich they are employed. For example, particle sizes within the desiredtarget range can provide targeted light filtering of radiation in thevisible and/or near infrared ranges of light. The particle size canimpact the light scattering depending on operating wavelength(s). Largerparticle sizes relative to the wavelength may induce a desiredscattering. Smaller particle sizes may be selected to reduce scattering.

If desired, a target concentration of the filler in the final extrudedcomposition can also be determined. Examples of suitable targetconcentrations include a range of 0.001 weight % to 30 weight %,relative to the total weight of the final extruded composition prior todrying. For certain applications, such as where transparency to visiblelight and/or light filtering effects are desired, it is desirable toemploy very low concentrations of filler as the target for the finalextruded composition prior to drying. For example, relatively low targetconcentrations can range from about 0.001 weight % to about 0.30 weight%, such as from about 0.01 weight % to about 0.15 weight %, relative tothe total weight of the final extruded composition prior to drying.Hitting a desired target particle size distribution and/or targetparticle concentration is difficult for such relatively lowconcentrations using traditional techniques. The techniques of thepresent disclosure allow these target particles size distributions andconcentrations to be realized.

The filler can be any desired filler to be incorporated into anextrudable matrix material. Examples include fillers chosen from carbonblack, carbon nanotubes, graphene, TiO2 and combinations thereof.Commercially available fillers often have an average particle size thatis larger than the target average particle size. The initial averageparticle size for the particles employed in the methods of the presentdisclosure can be, for example, any commercially available size.Examples of suitable particle sizes included particles ranging fromabout 20 nm to about 25 millimeters, such as about 800 nm to about 20millimeters, or about 1 micron to about 20 millimeters. The particlessizes may vary depending on the form of the particles. For instance, forparticles in a pelletized form, an initial average particle size mayrange from about 0.5 millimeters to about 25 millimeters, such as about1 millimeter to about 20 millimeters. For particles in a powder form,particle sizes can range, for example, from about 20 nm to about 500microns, such as about 30 nm to about 1200 nm. The ratio of the initialaverage particle size to the target average particle size can range, forexample, from about 1.5 to about 25,000,000.

For certain applications it may be desirable to produce a very uniformparticle size distribution using the techniques of the presentdisclosure. For example, it may be desirable to produce a distributionof particles in which 90% to 100% of the particles are within a givensize range, such as any of the target size particle ranges describedherein. In another example, it may be desirable to produce adistribution of particles in which 90% to 100% of the particles have aparticles size that is within 10% of a given size range, such as within10% of any of the target size particle ranges described herein. Theparticle sizes of commercially available fillers may not be sufficientlyuniform for such applications.

Employing a relatively high initial concentration of filler during theextrusion process can be a factor in controlling particle size of thefiller. This is because increased shear due to grinding of the particlesat the higher concentration can be applied to the filler duringextrusion at the higher concentrations, allowing filler particle size tobe reduced to a greater extent during the extrusion process than if thefiller were at lower concentrations. The resulting batches of extrudedmaterial with higher concentrations of filler can then be diluted withadditional polymer matrix material until the desired lower targetconcentrations of filler are realized. The additional polymer matrixmaterial can be added, for example, during one or more separateextrusion processes that are employed to intimately mix the polymermatrix material and the filler.

The initial concentration of filler can be any desired concentration,and may vary depending on the application. In one implementation, theinitial concentration of filler can be higher than the desired targetconcentration for the final extruded composition. As an example, theinitial filler concentration can range from about 0.01 weight % to about40 weight %, such as about 1 weight % to about 30 weight %, or about 0.1weight % to about 20 weight %, or about 0.1 weight % to about 2 weight%, relative to the total weight of the initial extrudable composition.

The extrudable compositions can include any suitable polymer matrixmaterial. Examples of suitable polymer matrix materials comprise atleast one polymer chosen from polycarbonates, Polyethylene terephthalate(“PET”), Polyethylene (“PE”), acrylate polymers, vinyl polymers,polyvinylbutyral (“PVB”) and a PVB copolymer. The PVB copolymer cancomprise polyvinylbutyral units and one or more of polyvinyl alcoholunits and polyvinyl acetate units. It is well known thatpolyvinylbutyral and the disclosed PVB copolymers have a closerefractive index with various types of glass and the ability to stick toglass and form a strong bond.

The polymer matrix material can be included in any suitable amount andmay vary depending on the application for which the final composition isto be used (e.g., optical filters, other optical elements or still otherapplications), as well as the number of extrusions to be performed toachieve the desired concentrations and the point in the process at whichthe extrusion is occurring. For example, in one implementation wheremultiple extrusion processes are to be performed, the initialconcentration of matrix material can be lower than the desiredconcentration for the final extruded composition. Examples of suitableamounts of polymer matrix material in the initial extrudable materialcan range from about 60 weight % to about 99.99 weight %, such as about90 weight % to about 98 weight %, relative to the total weight of theinitial extrudable composition. The concentration of polymer matrixmaterial in the final extruded product can be any desired concentration,such as, for example, a concentration ranging from about 90 weight % toabout 99.99 weight %, such as about 99 weight % to about 99.99 weight %,relative to the total weight of the final extruded composition.

The initial extrudable composition comprising a polymer matrix materialand the filler ingredients are introduced into an extruder, either priorto or subsequent to mixing the ingredients. The extruder can be anysuitable type of extruder than can provide the desired shear force toreduce the size of the filler particles, such as a twin screw extruderor a quad screw extruder.

The extrudable composition is then extruded to reduce the size of thefiller from the first average particle size to a reduced averageparticle size, thereby forming a second extrudable composition. Thereduced average particle size is within 10% of the target averageparticle size, as determined by SEM or other suitable microscopytechnique. As an example, the first extrudable composition is extrudedone or more times, such as 1 to 5 times, or 2 to 4 times, to reduce thesize of the filler to achieve a size that is sufficiently close to thechosen target average particle size. After each extrusion thecomposition can optionally be formed into extrudable pellets. Forexample, the extruded composition can initially be in the form of longstrands that are cut into pellets and dried to form a bulk extrudablematerial that is then employed as a starting material in subsequentextrusions.

The second extrudable composition can optionally be extruded with adiluent polymer one or more times, such as 1 to 5 times, or 2 to 4times, to dilute the concentration of the filler and optionally reducethe particle size of the filler further to thereby form a thirdextrudable composition having the desired target filler concentration.For example, the above described second extrudable composition havingthe reduced filler average particle size can be added to a secondextruder, which can be either the same extruder used to reduce theparticle size or a different extruder. Additional polymer matrixmaterial is also added to the second extruder, where the additionalpolymer can be the same or different than the PVB or PVB copolymersdescribed above. The combined second extrudable composition having thereduced filler average particle size and the additional polymer are thenextruded together to thereby dilute the concentration of filler and formthe third extrudable composition. This extrusion process and theaddition of polymer to the extrudable composition can be repeated anydesired number of times until the desired target filler concentration isreached. Thus, repeating the extrusion process in this manner canprovide the ability to achieve relatively low target concentrations offiller that is uniformly mixed in the composite compositions.

The extrusion processes for reducing the particle size and dilution ofthe particle filler concentration can be carried out in any desiredorder. For example, one or more extrusion processes can be carried outto reduce the particle size, followed by an extrusion process fordilution, followed by a further extrusion process to reduce the particlesize. As another example, a first extrusion process can be carried outto reduce the particle size and form a first batch of extrudablematerial, followed by a second extrusion process that dilutes the firstbatch by adding additional polymer matrix material and simultaneouslyreducing the particle size. If desired, the first batch can be formedinto pellets, as described herein, which are then employed with theadditional polymer matrix material as a starting material for the secondextrusion process.

Whether or not the size of the filler is reduced during extrusion and,if reduced, the resulting size of the particles after each extrusion,will depend on a number of factors. These factors include, for example,the type of filler, the type of polymer matrix material, initialconcentration of the filler in the extrudable material, the screwsetup/screw design in the extruder and other extruder conditions, suchas the temperature of extrusion zones and the type of die employed.Given the understanding provided by the present disclosure, includingthe above factors, one of ordinary skill in the art would be able tomodify the processes of the present disclosure in order to controllablyand repeatedly obtain the desired particle size distribution of thefiller in the extrudable material.

The present disclosure is also directed to a filter for filtering light.An example of a filter 110 is illustrated in FIG. 2. Filter 110comprises a support substrate 112. A film 114 is disposed on the supportsubstrate 112. Filter 110 optionally includes a second substrate 116,the film 114 being disposed between the support substrate 112 and thesecond substrate 116.

The filter can have linear or non-linear optical properties. Linearoptical properties are constant with the incident light intensity. Alinear filter transmits a fixed percentage of the incident lightindependent of the incident light intensity. For non-linear opticalproperties, the transmitted light varies with the intensity of incidentlight. As an example, in a non-linear filter, such as filter 110, underrelatively high incident light intensity, the particles of film 114absorb energy and can change form by dissociating or cause heating ofthe surrounding polymer matrix material, which in turn causes arefractive index change and subsequent scattering and blocking of light.This can be a passive process that, as an example, only occurs underrelatively high incident power.

Film 114 can be any of the extrudable compositions of the presentdisclosure comprising a polymer matrix material and filler. The polymermatrix material can be any of the polymers described herein. The fillercan be any of the fillers described herein and has a particle sizedistribution configured to filter a desired range of wavelengths oflight, including any of the particle sizes and/or particle distributionsdescribed herein for the extrudable compositions. The range ofwavelengths of light are selected from wavelengths in the visiblespectrum, the near infrared spectrum, and both visible and near infraredspectra. As an example, the filtered range of wavelengths of lightinclude wavelengths across the entire visible and near infrared (“NIR”)spectrum, where the filter is configured to uniformly reduce theintensity of light across the entire visible spectrum and the NIRspectrum. The amount of light reduction depends on the concentration offiller and the thickness of film 114. As an example, the reduction inlight intensity can range from 5% to 80%, or from 20% to 50%, or about30%, compared to the intensity of visible light incident on the filter.In an example, the filler employed in the film 114 has a reduced averageparticle size that is within 10% of any of the target average particlesizes, as described herein, and has a concentration ranging from 0.001weight % to 30 weight %, such as about 0.001 weight % to 0.30 weight %,or about 0.01 weight % to 0.15 weight %, relative to the total weight ofthe extrudable composition.

The film 114 can have any suitable thickness. For example, thicknessescan range from 1 nanometer to 1 centimeter, such as 1 micron to 1millimeter. The chosen thickness of the film can provide for a desiredlevel of transparency and/or light filtering. The film thickness can beuniform over the entire film. In another example, the thickness and/orfiller concentration of the film 114 can be varied across the lengthand/or width of the film in order to vary the amount of light intensityreduction across the film. In this manner, a filter having a lightintensity reduction gradient can be formed. Such gradients can be usedin certain optical applications, including corrective lenses, sunglassesand so forth.

One or both of the support substrate 112 and the second substrate 116are transparent to visible light. Any suitable materials transparent tovisible light can be employed. As an example, one or both of the supportsubstrate and the second substrate comprise at least one material chosenfrom glass and polycarbonate.

In one example implementation, the refractive index of the supportsubstrate and the optional second substrate are matched to be similar tothe refractive index of the film 114. As an example, the supportsubstrate 112 has a first refractive index, the film 114 has a secondrefractive index and the second substrate 116 has a third refractiveindex. Mismatch of the refractive index causes a reflection at theinterface (bondline) between the film and the substrate. An exact indexmatch between the film and the substrate will have no reflection. In anexample, the refractive index of one or both of the support substrateand optional second substrate match the film refractive indexsufficiently to avoid or reduce a reflection at the film/substrateinterfaces. For example, a ratio of the first refractive index to thesecond refractive index ranges from 0.9 to 1.1. A ratio of the thirdrefractive index to the second refractive index ranges from 0.9 to 1.1.

The support substrate 112 and second substrate 116 can have any suitablethicknesses that will provide the desired mechanical support andtransparency. For example, thickness of substrates 112 and 116 can eachrange from about 0.1 millimeter to about 50 millimeters, such as about0.5 millimeter to about 20 millimeters. The substrates 112, 116 can beplanar, as shown in FIG. 2, or can have any other desired shape, such ascurved, circular or spherical.

Film 114 can be deposited on support substrate 112 in any suitablemanner. Examples of suitable techniques include lamination and solutiondeposition methods. Lamination techniques, for example, can includeapplying heat and or pressure to the substrate/film/substrate stack.Examples of suitable lamination and other deposition techniques are wellknown in the art.

The present disclosure is also directed an extrudable composition. Thecomposition comprises a polymer matrix material and a fillerincorporated into the polymer matrix material. The filler has a reducedaverage particle size that is within 10% of any of the target averageparticle sizes, as described herein, and has a concentration rangingfrom 0.001 weight % to 30 weight %, such as about 0.001 weight % to 0.30weight %, or about 0.01 weight % to 0.15 weight %, relative to the totalweight of the extrudable composition. The composition can be extrudedinto long strands that are cut into pellets and dried to form a bulkextrudable material.

EXAMPLES

The extruder used in the examples below employed a 3 mm die, althoughany other die size could be used. For example, final products could bemade using a die that produces a sheet of appropriate thickness tolaminate between glass windows.

Materials used in the examples below include one or more of thefollowing:

-   -   Kuraray Mowital Polyvinyl Butryal (PVB) B45H and B60H: Polyvinyl        Butyral that includes plasticizers.    -   Akzo Nobel Ketjenblack EC-600 JD carbon black: This carbon black        is electrically conductive, highly branched, has a high surface        area of 1250 m²/g, and a density of 1.8 g/cm³. This carbon black        is in the form of pellets that are 100 μm to 2 mm in size that        upon mixing into a polymer easily separate into primary        aggregates 30 to 100 nm long.    -   Cabot Vulcan XC72 carbon black: (pelletized/beaded version that        is less fluffy that the XC72R version) This carbon black is        electrically conductive, has a surface area of 254 m²/g, a        primary particle size of 30 nm, and density of 1.8 g/cm³. This        carbon black is in the form of beads (˜1 mm) that upon mixing        into a polymer easily separate into primary aggregates 36 nm to        1122 nm long.

On the day of extrusion, the powder Kuraray Mowital Polyvinyl Butryal(PVB) B45H and B60H resin bags were opened and used immediately toprevent uptake of moisture. The carbon blacks were used as received.

Prior to extrusion, the screws were removed and cleaned. The extruderused was an American Leistritz Extruder Corporation Model ZSE 27. Thisextruder has a 27 mm co-rotating intermeshing twin screw with 10 zonesand a length/diameter ratio of 40. An AccuRate gravimetric feeder usedfor the polymer powder using a 1 inch open helix with a 1 inch insidediameter polyliner. FIG. 3 shows the extruder screw design used. In thisscrew design, the KS 3-2-10/30-90° N are 3 of KS1-2-10-M that are eachoffset 90° from each other. The polymer powder and EC-600 JD carbonblack were added at zone 1. A K-Tron KCL-SFS-KT-20 twin screwgravimetric feeder with a 2 blade agitator and concave fine screws wereused to feed the EC-600 JD. Water cooling was used on cooling of theextrusion zones.

After passing polymer through three 3 mm diameter holes of the extruder,the resulting polymer strands enter a water bath (˜80° F.) and then aConAir Model 20402HP-14A pelletizer that produced nominally 3 mm longpellets. For each formulation, approximately 2 pounds of pellets wereproduced. The formulations produced are listed below in Table 1. Afterextrusion, the pellets were allowed to dry at ambient conditions (23°C., 50% RH) for 2 days and then they were placed in sealed moisturebarrier bags.

TABLE 1 Extrusion Samples Sample Code Extrusion Run Description Example1 OB45 300 RPM = neat B45H PVB ran at 300 rpm extruder screw speedExample 2 OB45 400 RPM = neat B45H PVB ran at 400 rpm extruder screwspeed Example 3 OA1B45 1 wt % EC-600 JD in B45 H PVB Example 4 OA2B45 2wt % EC-600 JD in B45 H PVB Example 5 OA4B45 4 wt % EC-600 JD in B45 HPVB Example 6 OB60 300 RPM = neat B60H PVB ran at 300 rpm extruder screwspeed: these pellets had a trace amount of EC-600 JD in them but couldbe useful to examine to see what results we might get with extremely lowcarbon black loadings Example 7 OB60 450 RPM = neat B60H PVB ran at 450rpm extruder screw speed Example 8 OA1B60 1 wt % (really 1.3 wt %)EC-600 JD in B60H PVB Example 9 OA2B60 2 wt % EC-600 JD in B60H PVBExample 10 OA4B60 4 wt % EC-600 JD in B60H PVB Example 11 OX1B45 1 wt %(really 1.25 wt %- lowest we could go) XC72 in B45 H PVB Example 12OX2B45 2 wt % XC72 in B45 H PVB Example 13 OX4B45 4 wt % XC72 in B45 HPVB Example 14 OX1B60 1 wt % (really 1.6 wt %- lowest we could go) XC72in B60H PVB Example 15 OX3B60 3 wt % XC72in B60H PVB Example 16 OX4B60 4wt % XC72 in B60H PVB Example 17 OX7.5B45 7.5 wt % XC72 in B45H PVBExample 18 OX7.5B60 7.5 wt % XC72 in B60H PVB Example 19 OX1B452E 1 wt %XC72 in B45H PVB Example 20 OX1B602E 1 wt % XC72 in B60H PVB Example 21OX0.5B45E2 0.5 wt % XC72 in B45H PVB Example 22 OX0.15B45E2 0.15 wt %XC72 in B45H PVB

The nomenclature for Table 1 sample codes is as follows:

-   -   O=Optical Project    -   A=Akzo Nobel Ketjenblack EC-600 JD carbon black    -   X=Cabot Vulcan XC72 beaded (pelletized) carbon black    -   B45=B45H PVB    -   B60=B60H PVB    -   2E=used at the end of the formulation name: extruded twice    -   R=Replicate formulation

The pellets made from extrusion samples 3, 4, 11, 12 and 18-22 wereanalyzed using FIB-SEM. FIG. 4 shows the FIB-SEM analysis of carbonblack filled PVB pellets having a 1% carbon black in PVB, as made inExample 11 (OX1B45). The pellets with 1% fill of Example 11 were usedfor subsequent extrusion runs to produce a lower concentration of carbonblack by the addition of more PVB at loadings of 0.5% (Example 21),shown in FIG. 5 and 0.15% (Example 22), shown in FIG. 6. It was clearfrom the analysis of Examples 21 and 22 that there were still some largeaggregates of carbon black even at low concentrations.

In preparation for FIB-SEM analysis, the pellet samples were mounted ina cold set epoxy and allowed to cure overnight. The samples werepolished with Struers Abramin polishing unit through 320, 600, 1200, and4000 grit. A prepolish rotating lap for 30 s with 1 um alumina wasperformed, as was a Vibromat polish overnight with 0.05 um alumina. Thesamples were rinsed thoroughly with water, sonicated in RO water for 5minutes, rinsed thoroughly with water and sonicated again for 5 minutes.Aluminum foil was used to mask ½ of the sample and the sample was plasmatreated in oxygen at 300 W and 240 mTorr for 5 minutes. The foil wasremoved and the samples were then coated with platinum. The coatedsamples were ground and loaded into a Carl Zeiss CrossBeam AurigaFIB-SEM to examine the surface morphology. Magnifications (using thePolaroid 545 reference) of 5, 10, 25, 50, and occasionally 100 kX wereused to image the samples.

Particle Size Analysis in FIB-SEM Images included manually measuredsub-micron particle sizes with Image Pro Plus analysis software.Particles greater than 1 urn were not measured. Very small particleswere measured at high magnification and listed in the “high mag” columnof Table 2. Larger particles were measured at lower magnification andlisted in the “low mag” column. Only images of the plasma treatedsamples were examined to determine particle sizes.

Table 2 gives a somewhat qualitative measurement of the carbon blackparticle sizes in the samples that were measured from the FIB-SEM imagesthat were collected. Measurements were only made of particles that werenot large aggregates (1 micron or less) and were more regular in theirparticle size. There were two general sizes of submicron particles,those from 80 to 280 nm and those below 30 nm.

TABLE 2 Particle Size Analysis of Carbon Black in Extruded PVB Pellets(Minimum of 20 particle measured per sample image) High MagnificationLow Magnification Pellet Mean (nm) Median (nm) Mean (nm) Median (nm)Example 11 OX1B45 13 13 237 230 Example 21 OX0.5B45E2 17 17 265 246Example 22 OX0.15B45E2 15 14 144 122 Example 20 OX1B602E 17 17 161 156Example 8 OA1B60 19 18 104 110 Example 3 OA2B45 21 21 118 112 Example 12OX2B45 18 17 80 69 Example 18 OX7.5B60 266 236

The master batch of Example 11 (OX1B45R) had larger particle sizes ofabout 237 nm. Example 21, at 0.5%, had a particle size of about 265 nm,while Example 22 at 0.15%, had a smaller particle size at only about 144nm. Also looking at Table 2 and comparing the different results betweentypes of carbon black, the Akzo Nobel Ketjenblack EC-600 JD carbon blackappears to give a smaller particle size than the Cabot Vulcan XC72carbon black, but not in all cases, as in the case of Example 12(OX2B45) with a mean particle size of 80 nm.

Example 23

There are two primary methods to implement this material into cells: hotpressing and solvent softening. Either case employs the molding orextrusion of sheets closely approximating the final installed thickness.A hot pressing technique is employed in this example.

Thin sheets of the extruded material were made by pressing thePVB/Carbon Black pellets in a heated Carver hydraulic press. The pelletswere put between sheets of Teflon and slipped into the press heated to185° C., which was well above the glass transition, to soften thepolymer. The Teflon sheets had a texture similar to cloth and produce asomewhat diffused looking surface. A sample film of the 1% loading wasput between glass slides and returned to the heated press. The platenswere pressed together to allow the glass and polymer to warm to 185° C.before applying some pressure, about 500 lbs. The result was a film thatadhered to the glass on both sides. The pressing between slides produceda nearly bubble free laminate (this was a simple process so some bubbleswere included near the edges where the initial sheet varied inthickness). The 1% samples of Example 11, even in very thin sheets, werevisually opaque. The films produced were made thin enough to allow lighttransmission with the 0.5% and 0.15% carbon black loadings. The pressedsheet basic thickness was ˜0.009″ but included one thin section that wascloser to 0.003″.

The 0.15% loaded films are somewhat transparent in these thicknesses.FIG. 7 shows spectral transmission and FIG. 8 illustrates the calculatedspectral absorption coefficients for the three spots plus average andstandard deviation.

The results of the pressing procedure for 0.5% loaded PVB is shown inFIGS. 9 and 10. Due to the high carbon loading and relative thickness,some of the transmission values, particularly at short wavelengths, werein the noise and did not allow calculation of absorption coefficients.FIG. 10 shows the resultant curve for one of the noisy transmissioncurves. It can be seen that even the noisy curve could be extrapolatedinto the short wavelengths, following the same trend as the othercurves.

Some analysis was carried out to determine the effects of particleloading on transmission. At first glance it appeared that absorptioncoefficient was linearly related to particle loading. The ratio ofabsorption coefficients (within the current level of accuracy) was veryclose to the ratio of loading percent by weight and was nearly constantby wavelength, as shown by FIG. 11. Because the ratio of absorptioncoefficients was nearly constant across the wavelength region, thelinear relationship between the particle loading and absorptioncoefficient was determined using the band average absorption coefficientfor both the 0.15% and 0.5% particle loadings.

Plotting the particle loading versus Absorption Coefficient, (FIG. 12),the slope of the linear fit (assuming it is linear) was determined withthe absorption coefficient zero at a particle loading of zero. The slopeof the line was determined and predicted a particle loading that willgive a desired particle loading for the desired thickness from thecharted fit. However, the relationship was by default linear since onlytwo concentrations were compared, and Fresnel reflections of the samplewere not necessarily taken into account correctly in the initialabsorption coefficient calculations. It was noted that the real linearfit of the two data points did not go through the origins, which may bedue to the large errors in the initial transmission and thicknessmeasurements as shown by the large standard deviations in the absorptioncoefficients or the assumption of linearity.

As an example, if the above assumptions are correct, choosing a targetthickness of ˜0.4 mm for the film and a transmission of ˜40% results inan absorption coefficient (alpha) of 2.29. Based on that, a targetparticle concentration=0.0105*alpha can be calculated, based on the fitin FIG. 12, or approximately 0.025% loading by weight to achieve theabout 40% transmission for a 0.4 mm thick film.

Example 24

A filter was made by pressing a 0.15% carbon black PVB film betweenOptosil™ glass plates. The 0.15% loaded PVB film had a thickness of˜0.10 mm (˜0.004″). The resulting filter was sufficiently transparent sothat typed text could easily be read through the filter.

Example 25

An OX0.01B45E4 material was made from XC72 in B45H PVB using extrusiontechniques of the present disclosure. The batch was extruded four timesto reach the concentration of 0.01 wt %. A film was made from theOX0.01B45E4 material using hot pressing procedures similar to thosedescribed above for Example 23. The goal was to make a film havingcarbon black aggregates that are 0.14 to 0.22 μm.

Photomicrographs were collected at 50,000× magnification, 100,000×magnification and 200,000× magnification at 4 different locations of thefilm for each level of magnification. All images were acquired with aHitachi S-4700 field emission scanning electron microscope (FESEM). Theoperating conditions were 10 kV accelerating voltage with a 5 μAemission current. The working distance was 6 mm using the uppersecondary electron detector. Images were collected near the center fromtwo different pieces of flat film and two different through thethickness edges with image lock on. All images appeared to be similar.FIG. 13 shows an example photomicrograph collected at 50,000×magnification for the OX0.01B45E4 film of Example 25.

Image analysis images were also collected at 50,000× magnification onthe FESEM using a contrast of ˜60% and brightness ˜0%. FIG. 14 gives anexample of such a photomicrograph image used for image analysis at50,000× magnification. Image analysis was performed on 22 such imagesobtained by the FESEM at 50,000× magnifications on the OX0.01B45E4 filmof Example 25. The images were processed and measured using ImageJsoftware. The following steps were taken to process the images: 1) Imagewas converted from RGB (red green blue) to greyscale. 2) Image wasinverted to convert the background pixels from black to white and toconvert the aggregate pixels from white to black as demonstrated in FIG.15. 3) The scale bar was measured and scale was set to calibrate theratio of pixels to a known distance. 4) The scale bar and operatingconditions of the FESEM were cropped out of the image. 5) The image waschanged into a foreground (carbon black) in red and a background(matrix) in white. 6) Image analysis was conducted on all of the 22images 4 different times by varying the lowest carbon black particlearea measured from 300 nm² (Feret's diameter of 25 nm) to 1,000 nm²(Feret's diameter of 50 nm) to 2,800 nm² (Feret's diameter of 75 nm) andto 4,400 nm² (Feret's diameter of 100 nm). FIG. 16 shows the analysisconducted using the lowest carbon black area of 300 nm² so it analyzesFeret's diameter >25 nm. A total of 285 carbon black particles (shownhaving a number on them in FIG. 16) were measured. As the smallestcarbon black area measured increases, the number of particles analyzeddecreases. Particles that touch the edges of the image were not counted.

ImageJ image analysis software was used to measure perimeter, length,width, aspect ratio, circularity, and the Feret's diameter of eachcarbon black particle. The perimeter was the length of the outerboundary of the particle. The length and width of the particles weremeasured by fitting ellipses to the particles and measuring the majorand minor axes, respectively. The major axis was the longest diameter ofthe fitted ellipse and the minor axis was the shortest diameter of thefitted ellipse, as shown in FIG. 17. The aspect ratio was calculated bydividing the major axis by the minor axis for each particle. Circularitywas calculated using Equation 1. A circularity of 1 represents a perfectcircle. FIG. 18 shows circularity values for some of the actual carbonblack images. The Feret's diameter is the measurement of the furthestdistance between any two parallel tangents on the particle, as shown inFIG. 19.

$\begin{matrix}{f_{circ} = \frac{4\pi\; A}{P^{2}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$where:

-   -   A=Area of particle    -   P=Perimeter of particle

Table 3 summarizes the image analysis results (mean±standard deviation)for the various threshold areas used. A mean Feret's diameter of 0.158μm was obtained using a threshold area of 4,400 nm² and a mean Feret'sdiameter of 0.133 μm was obtained using a threshold area of 2,800 nm²,which are close to a desired range of 0.14 to 0.22 μm. It was assumedthat any particles smaller than 25 nm were likely not carbon black forthese calculations.

TABLE 3 Measurements (mean ± standard deviation) of shape descriptors ofparticles using image analysis on ImageJ software for differentthresholds of carbon black particle areas. Threshold Area (nm²)Perimeter (μm) Length of Major Axis (μm) Length of Minor Axis (μm)Circularity Feret's Diameter (μm)$( \frac{{AR}\mspace{14mu}{major}}{minor} )$ N   300 0.286 ±0.074 ± 0.042 ± 0.492 ± 0.086 ± 1.819 ± 5,399 0.231 0.042 0.021 0.1870.053 0.632 1,000 0.363 ± 0.091 ± 0.051 ± 0.448 ± 0.106 ± 1.814 ± 3,7590.238 0.039 0.018 0.170 0.051 0.569 2,800 0.476 ± 0.112 ± 0.062 ± 0.368± 0.133 ± 1.858 ± 2,171 0.257 0.038 0.016 0.141 0.052 0.609 4,400 0.593± 0.130 ± 0.070 ± 0.309 ± 0.158 ± 1.912 ± 1,229 0.287 0.041 0.016 0.1220.056 0.665

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. In addition, while a particular feature of thepresent teachings may have been disclosed with respect to only one ofseveral implementations, such feature may be combined with one or moreother features of the other implementations as may be desired andadvantageous for any given or particular function. Furthermore, to theextent that the terms “including,” “includes,” “having,” “has,” “with,”or variants thereof are used in either the detailed description and theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising.” Further, in the discussion and claims herein, theterm “about” indicates that the value listed may be somewhat altered, aslong as the alteration does not result in nonconformance of the processor structure to the intended purpose described herein. Finally,“exemplary” indicates the description is used as an example, rather thanimplying that it is an ideal.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompasses by the following claims.

What is claimed is:
 1. A method of controlling a particle sizedistribution of a filler in an extrudable composition, the methodcomprising: introducing an extrudable composition comprising a polymermatrix material and a filler into an extruder, the filler having a firstaverage particle size that is larger than a target average particlesize; and extruding the extrudable composition one or more times usingthe extruder to reduce the size of the filler from the first averageparticle size to a reduced average particle size, the reduced averageparticle size being within 10% of the target average particle size,wherein a final concentration of the filler ranges from about 0.001weight % to less than 1 weight %, relative to the total weight of theextrudable composition.
 2. The method of claim 1, wherein the finalconcentration of the filler ranges from about 0.01 weight % to about0.15 weight %, relative to the total weight of the extrudablecomposition.
 3. The method of claim 1, wherein the first averageparticle size ranges from about 20 nm to about 25 millimeters.
 4. Themethod of claim 1, wherein the target average particle size ranges fromabout 1 nm to about 700 nm.
 5. The method of claim 1, wherein a ratio ofthe first average particle size to the target average particle sizeranges from about 1.5 to about 25,000,000.
 6. The method of claim 1,further comprising diluting the filler in the extrudable composition tothe final concentration.
 7. The method of claim 6, wherein the dilutingcomprises adding a diluent polymer to the extrudable composition andrepeating the extruding one or more times, the diluent polymer being thesame as the polymer matrix material.
 8. The method of claim 7, furthercomprising repeating the extruding one or more times to further reducethe average particle size of filler.
 9. The method of claim 8, furthercomprising forming the extrudable composition into pellets after eachextruding.
 10. The method of claim 1, wherein the polymer matrixmaterial comprises at least one polymer chosen from polycarbonates,Polyethylene terephthalate (“PET”), Polyethylene (“PE”), acrylatepolymers, vinyl polymers, polyvinylbutyral (“PVB”) and a PVB copolymer,the PVB copolymer comprising polyvinylbutyral units and one or more ofpolyvinyl alcohol units and polyvinyl acetate units.
 11. The method ofclaim 1, wherein the filler is chosen from carbon black, carbonnanotubes, graphene, TiO₂ and combinations thereof.
 12. The method ofclaim 1, wherein the final concentration of the filler ranges from 0.01weight % to 0.3 weight %.
 13. A method of controlling a particle sizedistribution of a filler in an extrudable composition, the methodcomprising: determining a target average particle size for the filler;determining a target concentration of the filler; introducing a firstextrudable composition comprising a polymer matrix material and thefiller into an extruder, the filler having a first average particle sizethat is larger than the target average particle size, the filler beingat a concentration ranging from about 0.01 weight % to about 40 weight%, relative to the total weight of the extrudable composition; extrudingthe first extrudable composition one or more times to reduce the size ofthe filler from the first average particle size to a reduced averageparticle size to thereby form a second extrudable composition, thereduced average particle size being within 10% of the target averageparticle size; and extruding the second extrudable composition with adiluent polymer to dilute the concentration of the filler to form athird extrudable composition having the target concentration.
 14. Themethod of claim 13, wherein the first average particle size ranges fromabout 20 nm to about 25 millimeters.
 15. The method of claim 13, whereinthe target average particle size ranges from about 1 nm to about 700 nm.16. The method of claim 13, wherein the filler in the first extrudablecomposition is at a concentration ranging from about 0.1 weight % toabout 40 weight %, relative to the total weight of the first extrudablecomposition.
 17. The method of claim 13, wherein the target averageparticle size ranges from about 10 nm to about 500 nm.
 18. The method ofclaim 13, wherein a ratio of the first average particle size to thetarget average particle size ranges from about 1.5 to about 25,000,000.19. The method of claim 13, wherein the target filler concentrationranges from 0.001 weight % to 30 weight %.
 20. The method of claim 13,wherein the target filler concentration ranges from 0.001 weight % to0.3 weight %.
 21. The method of claim 13, wherein the diluent polymer isthe same as the polymer matrix material.
 22. The method of claim 13,where the extruding of the first extrudable composition is carried out 2to 5 times.
 23. The method of claim 13, wherein the polymer matrixmaterial comprises at least one polymer chosen from polycarbonates,Polyethylene terephthalate (“PET”), Polyethylene (“PE”), acrylatepolymers, vinyl polymers, polyvinylbutyral (“PVB”) and a PVB copolymer,the PVB copolymer comprising polyvinylbutyral units and one or more ofpolyvinyl alcohol units and polyvinyl acetate units.
 24. The method ofclaim 13, wherein the filler is chosen from carbon black, carbonnanotubes, graphene, TiO₂ and combinations thereof.